Chapter 1 – The Adopted Fiancé in the World of Oregairu!
Youth.
A word so familiar, yet somehow distant.
It's like a fleeting dream—beautiful while it lasts, but gone without a trace once you awaken.
Spring is the youth of the year, just as youth is the spring of life.
But time never waits. The moment you start hesitating, putting things off, the opportunity slips away. That beautiful girl in her twenties, the one you could've kissed? Gone. Grass withers. Trees shed their leaves. Youth fades faster than we realize.
This is the so-called "freest" period in one's life—where you're allowed to succeed or fail, to try or stumble. But regardless of the outcome, the memories become precious treasures in the future.
"...A ceiling I don't recognize."
That was Shin Akira's first conscious thought as he opened his eyes again.
He was lying in bed. Slowly lifting the blanket, he sat up and scanned the room. The furniture, the interior design—it all screamed modern era. Not an isekai. Not a fantasy world. Definitely not ancient times.
A wave of fatigue coursed through his body. Akira furrowed his brow.
Then it clicked.
His third transmigration had begun.
The second one had officially ended. This was now his third world.
Just like before, his powers were sealed once again. He was back to being an ordinary human.
Even though he had gone through this cycle of rising and falling in power, the sensation still left a bitter taste in his mouth.
Just before he departed from the previous world, something... intimate had finally happened with the goddess he'd been with. It wasn't just a glance, a hug, or innocent affection—they had truly become one.
Shin Akira was now officially "the man of a goddess."
Before leaving, he entrusted his [Boosted Gear: Red Dragon Emperor Gauntlet] to her.
It was his promise to Ddraig—to help with the dragon's reincarnation. And to Hephaestus, as a parting gift, Akira granted her unrestricted access to the [Shadow Realm], along with full command over the Nine Legions of the Shadowkhan.
But this time, unlike his previous transmigrations, the system had actually given him a new identity.
And once the information sank in, Akira's face twisted in disbelief.
His new name was Yukinoshita Akira.
Yes—that Yukinoshita. The one from the Oregairu universe.
In the previous High School DxD world, he had even uploaded and sold Oregairu novels for money. Who would've thought he'd actually end up in that very world?
The biggest facepalm, however, was this—he had now transmigrated into a slice-of-life world.
Three seasons of anime. All about love, friendship, and awkward teenage drama.
In this new life, he wasn't a biological Yukinoshita. He was an orphan who had been adopted by the family.
Why? Simple.
He was adopted to be a groom—married into the Yukinoshita bloodline.
The prestigious Yukinoshita family had two daughters. In order to preserve their legacy, they needed a male heir. The solution? Adopt a boy and marry him off to one of their daughters.
In other words, Akira was the adopted fiancé.
And the one he was promised to?
The eldest daughter, Yukinoshita Haruno.
The Yukinoshita family had a rather... unique approach to raising children. Haruno, the eldest, was raised in an environment of strict discipline—her personality, conduct, and even appearance had to be immaculate.
She was raised to be the perfect successor. The image of the ideal lady. A flawless leader.
Yukino, on the other hand, was left to grow freely—almost like a neglected housecat. As long as she stayed alive, it was enough.
The family only needed one heir. The second child? Merely a tool for marriage alliances.
And so, the two sisters grew up to be complete opposites.
Haruno, the elder sister, sparkled on the outside—warm, cheerful, and sociable. But beneath the surface, she was cold, calculating, and wore a mask of perfection.
Yukino, the younger, was a perfectionist with a kind heart. Though she was sharp-tongued and icy on the outside, deep down she cared deeply and held fast to her ideals and sense of justice.
Akira's position in the household was... complicated.
Though only a childhood fiancé, both Mr. and Mrs. Yukinoshita didn't control his life too strictly.
As long as he didn't break the family's core principles, they rarely interfered.
In fact, he arguably had more freedom than Haruno or Yukino combined.
According to the background given by the system, Akira was younger than Haruno and the same age as Yukino. Both girls were currently second-year students at Sobu High.
Yukino was in Class 2-J, the international elite course.
Akira? Class 2-F—the same one as the infamous "Great Teacher" and the "Dango Girl."
Right now, he lived in a rented apartment—not the Yukinoshita estate.
And wouldn't you know it—the unit next door belonged to Yukino. A fact that, of course, was arranged by Haruno.
After sorting through all this information, Akira could only sigh and rub his temples.
Seriously… how the hell was he supposed to increase Template Inheritance Progress in a world like this?
As if responding to his frustration, the system voice echoed softly in his mind:
[Ding!]
[Host has successfully transmigrated to a testing world. Would you like to select your Inheritance Template now?]
"Begin."
A familiar interface appeared. Templates began cycling across the translucent screen in front of him—until finally, it stopped.
A man wielding a crimson katana appeared.
[Ding!]
[Congratulations! Host has acquired Template: Yoriichi Tsugikuni!]
[Yoriichi Tsugikuni – The strongest swordsman in history. Beloved by the gods. Creator of the Breathing Techniques. Born with the Demon Slayer Mark and Transparent World.]
[Ding!]
[Congratulations! Host has obtained Talent: Demon Slayer Mark!]
[Ding!]
[Congratulations! Host has obtained Talent: Swordmastery Divine Path!]
Akira was stunned.
This time, the template he received… was the legendary swordsman from Demon Slayer—Yoriichi Tsugikuni?
He didn't possess the destructive godlike powers of a divine being, but in his world, Yoriichi stood at the absolute peak. A true legend.
Still... in this kind of peaceful, modern world… how was he supposed to raise his inheritance percentage?
Was he supposed to practice sword swings in the park every day?
There weren't even any demons to fight here.
Despite the many doubts swirling in his mind, Akira couldn't help but feel that getting this template was still a blessing.
He now held the strength of Enkidu, the command of the King of the Shadowkhan, and the swordsmanship of Yoriichi Tsugikuni.
If all three were combined...
Then Shin Akira's power would transcend anything he'd ever achieved before.
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